The present invention relates to locks and locking methods, and more particularly to devices and methods for locking and unlocking vehicle steering columns.
Numerous devices and methods exist for locking a vehicle steering column from movement. Most commonly, such devices and methods prevent the steering column from being rotated to steer the vehicle. The vehicle can be a car, van, truck, motorcycle, bus, or all-terrain vehicle having a number of wheels, a boat with one or more rudders, a snowmobile with skis, a vehicle having one or more tracks, and the like. A steering column lock used in any such vehicle is typically employed to prevent vehicle theft or unauthorized use.
A popular and well-known mechanism for locking a steering column is a lock bolt that is spring-loaded into direct or indirect releasable engagement with the steering column. Such engagement can be by removable insertion of the lock bolt into a groove, a notch, teeth, or an aperture in the steering column or in a gear, plate, or other element connected to the steering column. A mechanism is normally provided for retracting the lock bolt against the spring-loaded force to unlock the steering column for vehicle operation. As is well known to those skilled in the art, the mechanism can retract the lock bolt in response to user insertion and turning of a key or in response to one or more signals from a control system coupled to an actuator driving the mechanism.
Common design concerns with steering column locks include the ability of a lock to reliably lock the steering column and protection against the lock bolt engaging and locking the steering column during vehicle operation. For example, the lock bolt of a steering column lock should be able to properly extend and engage with the steering column (or element connected thereto as described above) even when the steering column is being turned. As another example, a familiar problem with many conventional steering column locks is the ability of a user to turn an inserted ignition key when turning force exists upon steering column from the front wheels of the vehicle. After the lock bolt has been inserted into the groove, notch, teeth, aperture and the like in its extended and locked position, a turning force from the front wheels can bind the lock bolt in this position. Typically, the user must turn the steering wheel to release the binding force upon the lock bolt in order to turn the ignition key, retract the lock bolt, and thereby unlock the steering column.
While lock bolt binding is not necessarily a critical design flaw in conventional manually-actuated steering column locks, it can be much more significant in newer steering column locks that are not mechanically connected to an ignition lock cylinder for actuation thereby. With the introduction in recent years of vehicle security systems in which a steering column lock is locked and unlocked by an electronic controller connected to one or more steering column lock actuators, there is little need to locate a vehicle""s ignition control (e.g., switch, button, and the like) adjacent to the steering column lock. The ignition control can be directly or indirectly connected to the steering column lock by wiring alone, and therefore can be located almost anywhere in the vehicle. However, without the ability of a user to mechanically manipulate the lock bolt as in most older steering column lock designs described above, reliable lock bolt disengagement can be a significant problem, particularly when the lock bolt is subjected to binding forces.
Other design concerns with steering column locks include lock complexity and lock manufacturability. Conventional steering column locks typically fail to address these concerns well. By way of example only, many steering column locks are assembled from a relatively large number of parts connected and fastened together in a time-consuming and expensive assembly process. In addition, little concern is normally paid to the complexity of the parts in many conventional steering column locks, thereby significantly increasing the manufacturing costs and end prices of such locks. Lock complexity can also lead to increased potential for lock assembly errors, operational problems and even malfunction.
In light of the problems and limitations of the prior art described above, a need exists for a steering column lock that is relatively simple, is easy and relatively inexpensive to manufacture and assemble, does not require mechanical actuation by a user, can be controlled and operated electronically, reliably locks the steering column even if rotating, and reliably unlocks the steering column even if the lock bolt is subjected to binding forces. Each preferred embodiment of the present invention achieves one or more of these results.
Preferred embodiments of the present invention have a lock bolt that is extendible and retractable by movement of a power transmission assembly. In some preferred embodiments of the invention, the power transmission assembly is rotatable by an actuator and has a cam thereon which engages a cam follower coupled to the lock bolt to retract the lock bolt and unlock the steering column. By employing a worm and worm gear set connecting the actuator to the power transmission assembly, the power transmission assembly can be provided with sufficient torque to extract the lock bolt even if held by relatively strong binding forces. The steering column lock of this preferred embodiment therefore does not require a user to reduce the binding forces upon the lock bolt (e.g., turn the steering column) prior to unlocking the lock assembly. Also, the steering column lock can therefore be located any distance from the vehicle""s user-manipulatable ignition control and need not be mechanically connected thereto.
The lock assembly of most highly preferred embodiments of the present invention can preferably be controlled by activation and deactivation of the actuator to permit the lock bolt to extend in a locking operation and to extract the lock bolt via the power transmission assembly in an unlocking operation. Preferably, one or more sensors directly or indirectly connected to the actuator can be used to trigger deactivation of the actuator when the lock bolt has been sufficiently moved to its locked and unlocked positions. Although the sensors can be positioned to detect a number of different moving elements in the lock assembly in a number of different manners, highly preferred embodiments employ mechanically-tripped sensors positioned adjacent to the cam and tripped by rotation of the cam at cam positions corresponding to extended and retracted positions of the lock bolt.
In some preferred embodiments, the cam has a curved surface with varying distance from the axis of rotation of the cam or pivot. The cam therefore produces smooth and controlled lock bolt camming action with little to no jarring motion (which can reduce the life of a lock bolt assembly). The cam preferably has a rotund shape such as an elliptical, round, or egg shape, and most preferably has an oval shape with initial and trailing ramping surfaces and a steeper intermediate ramping surface upon which the lock bolt rides at least when moving to an unlocked position. This cam shape provides superior lock bolt extraction even in binding conditions of the lock bolt.
In order to significantly reduce manufacturing and assembly time and cost of the steering column lock, some or all of the power transmission assembly is preferably assembled prior to being installed in a lock assembly frame. In some preferred embodiments, the power transmission assembly includes a pivot pivotably mounted to the frame and upon which are located a gear for transmitting driving power from the actuator to the pivot and a cam for transmitting rotational power from the pivot to the lock bolt. In such embodiments, the gear and/or the cam are preferably mounted upon the pivot to define a power transmission assembly that can be mounted upon the frame as a single unit. More preferably, the gear and/or the cam are integral with the pivot for this same purpose, thereby further reducing assembly and manufacturing time of the present invention. In those embodiments employing bearings for pivotably mounting the power transmission assembly, the bearings can also be assembled upon the pivot or can be made integral therewith prior to installation of the power transmission assembly as just described.
Preferably, part or all of the lock assembly can be assembled without turning, flipping, or otherwise re-orienting the lock assembly during the assembly process. To this end, some or all of the lock assembly components are preferably installed in the lock assembly from the same side of the lock assembly. In one highly preferred embodiment for example, all of the lock assembly components are mounted upon the frame from one side thereof, including the pivot, cam, and worm gear of the power transmission assembly, the lock bolt, the actuator and worm connected thereto, sensors for controlling deactivation of the actuator, and a lock assembly cover. This manner of assembly simplifies assembly operations, increases the speed at which the present invention can be assembled, reduces assembly error, and can therefore significantly reduce the cost of the lock assembly.
The present invention therefore provides an apparatus and method for locking a steering column that is simple in construction, is fast and easy to manufacture and assemble, can be controlled and operated electronically, reliably functions to lock and unlock the steering column of a vehicle, and can be employed in applications where no mechanical connection exists between a manually actuated ignition and the steering column lock or where a manually actuated ignition does not exist at all. More information and a better understanding of the present invention can be achieved by reference to the following drawings and detailed description.